Identification of a 13-kDa protein associated with the polyhydroxyalkanoic acid granules from Acinetobacter spp.

Abstract Transferrin-binding proteins from Neisseria meningitidis vary among different isolates. We have identified and studied a hypervariable region adjacent to the carboxyl-end of the transferrin-binding domain of the Tbp2 molecule. The tbp2 genes from six strains of N. meningitidis were cloned and sequenced in this particular region. Sequence analysis of these regions along with five other sequences available from pathogenic Neisseria showed a common organisation of seven highly variable nucleotide stretches interspersed with six conserved nucleotide stretches. The variable regions correlated with the location of immunoreactive epitopes in polyclonal antisera raised to transferrin-binding proteins identified by peptide pin technology. Sequence analysis suggested a mosaic-like organisation of the tbp2 genes. Taken together, these data suggest that the antigenic variation in this part of the protein may result from a strong host immune pressure.     

Isomerization ofn- andi-butyrate in anaerobic methanogenic systems

Studies of the degradation of the two isomeric forms of butyrate in different anaerobic environments showed isomerization betweenn- andi-butyrate. Degradation rates were similar for the different examined systems and degradation rates forn-butyrate degradation were generally higher than fori-butyrate. Degradation rates forn-butyrate ranged from 0.52 to 1.39 day^–1, while the rates fori-butyrate were from 0.46 to 1.15 day^–1. Production of isomers was not observed when the volatile fatty acid degradation was inhibited by addition of bromoethane sulfonic acid, indicating that isomerization was coupled to the methanogenic degradation of the acid. The degree of isomerization observed duringn-butyrate degradation was similar to the degree duringi-butyrate degradation. Experiments indicated that the isomerization degree was higher for the thermophilic than for the mesophilic inocula.     

Properties of aspartate racemase, a pyridoxal 5'-phosphate-independent amino acid racemase.

Aspartate racemase from Streptococcus thermophilus contains no pyridoxal 5'-phosphate or other cofactors such as FAD, NAD+, and metal ions. It was affected by neither carbonyl reagents such as hydroxylamine nor sodium borohydride but was strongly inhibited by iodoacetamide and other thiol reagents. Aspartate, cysteate, and cysteine sulfinate were the only substrates. The Km values for L- and D-aspartate were 35 and 8.7 mM, respectively. The enzyme catalyzed the exchange of alpha-hydrogen of the substrate with the solvent hydrogen. Racemization of L-aspartate in 2H2O showed an overshooting in the optical rotation of aspartate before the substrate was fully racemized. This shows that the removal of alpha-hydrogen of the substrate is at least partially rate-determining. When L- or D-aspartate was incubated with aspartate racemase in tritiated water, tritium was incorporated preferentially into the product enantiomer. The results strongly suggest that aspartate racemase contains two hydrogen acceptors.     

Features of changes in bioelectric reactions of the cerebral cortex in rats with deafferentation pain syndrome]

In rats with pain syndrome after sciatic nerve section the authors studied spontaneous and evoked bioelectric activity in sensomotor cerebral cortex of both hemispheres. Electrocorticogram showed the presence of hyper-synchronic discharges and paroxysmal peak-wave (700-800 mV) activity in contralateral hemisphere. While stimulating the injured limb the threshold of evoked potentials (EP) was observed to decrease, its amplitude to increase and focus maximum EP activity to extend.     

Effect of nonenzymatic glycation on the structure of immunoglobulin G

Incubation of human immunoglobulin G with glucose in vitro leads to covalent incorporation of the sugar concomitant with marked changes in molecular structure. After six to ten days of glucose incubation, absorption at 350 nm and fluorescence at 440 nm upon excitation at 370 nm markedly increased, indicating formation of nonenzymatic browning products. Furthermore, immunoglobulin G derivatives of a molecular mass of 500,000 Da appeared during glucose incubation as revealed by gel filtration. Electrophoretic examination of the 500-kDa protein revealed the formation of covalently bound immunoglobulin G polymers. Compared with nonglycated monomeric immunoglobulin G, functional properties of the 500-kDa protein, such as binding of protein A and fixation of complement are markedly reduced.     

Haemoglobin, serum albumin and transferrin variants of Bali (Banteng) cattle, Bos (Bibos) javanicus

1. Individual blood samples from 144 Bali (Banteng) cattle [Bos (Bibos) javanicus] in the Northern Territory of Australia and from 61 Bali cross cattle, were examined by zone electrophoresis to determine the variants of haemoglobin, serum albumin and transferrin that are present. 2. Of the common cattle haemoglobin variants (A and B) only variant B occurs in the Bali cattle samples. A second variant, designated CBali, occurs in Bali cattle either as the heterozygote (B CBali) or as the homozygote, the frequencies of occurrence indicating a two-allele system of inheritance without dominance. The CBali cross samples may exhibit the homozygous or heterozygous A variant. 3. The CBali variant has an electrophoretic mobility intermediate between those of the A and B variants at pH 8.6 and 9.1 but closer to B than to A (B greater than C greater than A). It appears to be similar in mobility to the C variants found in Indian Khillan (CKhillan) by Naik, Sukumaran and Sanghvi (Anim. Prodn, 1965 I, 275-277), and in Asian cattle by Oishi, Abe and Namikama (Immunogenet. Lett., 1968 5, 170-173) and Abe, Mogi, Oishi, Tanaka and Suzuki (Proc. XIIth Europ. Conf. Anim. Blood Groups Biochem. Polymorphisms 1972, pp. 225-228), but appreciably different from those in Kenyan and Rhodesian cattle (CRhodesia) found by Braend (Anim. Blood Grps Biochem. Genet., 1971 2, 15-21) and Carr (Rhod. J. agric. Res., 1964 3, 62-62A), respectively. It is also different in mobility from the C variant found by Winter, Mayr, Schleger, Dworak, Krutzler and Burger (Res. vet. Sci., 1984 36, 276-283) in the mithun.(ABSTRACT TRUNCATED AT 250 WORDS)     

Sequence-selective topoisomerase II inhibition by anthracycline derivatives in SV40 DNA: relationship with DNA binding affinity and cytotoxicity

Topoisomerase II mediated double-strand breaks produced by anthracycline analogues were studied in SV40 DNA. The compounds included doxorubicin, daunorubicin, two doxorubicin stereoisomers (4'-epimer and beta-anomer), and five chromophore-modified derivatives, with a wide range of cytotoxic activity and DNA binding affinity. Cleavage of 32P-end-labeled DNA fragments was visualized by autoradiography of agarose and polyacrylamide gels. Structure-activity relationships indicated that alterations in the chromophore structure greatly affected drug action on topoisomerase II. In particular, removal of substituents on position 4 of the D ring resulted in more active inducers of cleavage with lower DNA binding affinity. The stereochemistry between the sugar and the chromophore was also essential for activity. All the active anthracyclines induced a single region of prominent cleavage in the entire SV40 DNA, which resulted from a cluster of sites between nucleotides 4237 and 4294. DNA cleavage intensity patterns exhibited differences among analogues and were also dependent upon drug concentration. Intensity at a given site depended on both stimulatory and suppressive effects depending upon drug concentration and DNA sequence. A good correlation was found between cytotoxicity and intensity of topoisomerase II mediated DNA breakage.